Immersion oil is used to increase the resolution of a microscope by immersing both the objective lens and the specimen in a transparent oil of high refractive index
Nikon manufactures two types of Immersion Oil for microscopy these being Type A and Type NF. These oils are tested using Nikon objectives and therefore the performance cannot be guaranteed against lenses manufactured by other companies. The refractive indices of other manufactured oils may differ which will impair the results gained from using these with Nikon objectives. It is also important to note that oils should not be mixed as this will impair the performance.
Type A is general purpose oil used for imaging applications requiring oil immersion, which can incorporate techniques such as brightfield, darkfield, phase and fluorescence. It is available in three sizes of 8ml, 50ml and 500ml, all supplied with a pipette for dispensing. Type NF is considered to be the superior grade specifically designed for the ever growing need to improve signal to noise ratios in fluorescence microscopy, particularly in low-light applications or those between 340-380nm, typically associated with calcium or deep UV imaging. The improved quality is due to the type of raw materials used in the oil which relates to a subsequent reduction of auto fluorescence caused by minerals in the oil. There is one size available at 50ml, which is supplied with a plastic pipette for dispensing. It is slightly more viscous and has a slight odour.